This invention relates to devices which employ regenerative ion feedback for sustained electron emission, and particularly to structures and methods for controlling the output of such devices.
Display devices have been proposed in which electron multipliers operated in a regenerative ion feedback mode are used to provide current to light up a cathodoluminescent screen. For example, see U.S. Pat. No. 3,904,923 entitled "CATHODOLUMINESCENT DISPLAY PANEL," issued Sept. 9, 1975 to J. Schwartz. In one such structure, the electron multiplier includes at least two vanes having a plurality of parallel dynodes disposed in staggered relation thereon with a cathode at one end. This structure is further described in copending application Ser. No. 672,122, filed Mar. 31, 1976, entitled, "PARALLEL VANE STRUCTURE FOR A FLAT DISPLAY DEVICE." In this structure, electrical potentials of increasing magnitude are provided to the successive multiplying dynodes so as to produce an electron beam at the multiplier output. Generally, the electron multiplier has an open structure to allow feedback of ions which results in sufficiently high loop gain to produce sustained electron emission.
In one form of the previously described display device, display modulation is achieved by placing the necessary electrical potential on electrodes which are disposed near the multiplier output at a point between the multiplier and the cathodoluminescent screen. One problem with such a structure is that the electron multiplier must include filter structure to prevent high energy electrons from reaching the multiplier output. Otherwise, these high energy electrons would require extremely high voltages for acceptable modulation. Thus, it would be desirable to develop a structure and method for modulating a display device which employs regenerative ion feedback.